The invention is directed to optical devices. With the advent of semiconductor devices and applications thereof, GaN materials are being used for fabricating light emitting diodes (LEDs), lasers, and other types of devices. Typically, LEDs are formed over sapphire, silicon carbide, and on gallium nitride (GaN) substrates.
To form devices (e.g., LED or laser devices) over a GaN substrate, it is desirable to have a smooth surface. In the past, various processing techniques have been developed to achieve this goal. Unfortunately, conventional techniques have been inadequate.